The present invention relates to muscle stimulation using electrical impulses and, in particular, to a method of stimulating muscles in a cast-immobilized limb as a means of inhibiting muscle atrophy.
For bone fractures of different kinds, conventional medical treatment includes the immobilization of the portions of the body proximate the injury. This is often accomplished by using a cast, which is the simplest and crudest method of protecting an injury. The cast allows virtually no movement at all and is widely used to insure against reinjury. The impairment of movement is of particular importance in the repair and/or union of bone fractures.
Unfortunately, this method of protecting the injury often does not provide adequate means for exercising the body portions proximate the injury. For instance, a cast is often not strong enough, without additional reinforcement, to permit isometric exercising.
It is known that both muscles and bones should be exercised to prevent atrophy and maintain strength. When an individual sustains a physical injury which involves damage to bones, muscle tissue, connective tissue or the like, it is usually highly desirable for the muscle in the vicinity of the injury to be exercised in a controlled manner within specific parameters wherein the injured bone and/or tissue will remain stable. Unfortunately, however, the physician is generally unable to obtain adequate information or assurances about the manner in which a particular patient will conduct prescribed exercise. The physician does not know how much stress the patient can or will exert voluntarily, and does not know how well the patient will adhere to a schedule of repetitive exercise events. Unsupervised exercise is likely to deleteriously affect the injured tissues, thereby increasing the healing time, and sometimes causing irreparable damage. Furthermore, in most instances, the severity of the injury coupled with the rigidity of the cast render impossible the exercise of the muscles disposed thereunder.
One promising direction is to activate the affected muscles using electrical stimulation. There exist several devices for electrical stimulation of injured tissue situated underneath a cast. U.S. Pat. No. 4,574,809 to Talish, et al., entitled: xe2x80x9cPortable Non-Invasive Electromagnetic Therapy Equipmentxe2x80x9d, teaches a cast-embeddable coil structure which includes a single connector fitting, designed for exposure externally of a completed cast and for removable mounting and electrical connection to a self-contained light-weight rechargeable portable signal-generator unit. The signal-generator unit is mounted to the cast only for periods of therapeutic treatment, and is removably mounted to a less-portable charging unit in intervals between periods of therapeutic treatment.
U.S. Pat. No. 4,998,532 to Griffith, entitled xe2x80x9cPortable Electro-Therapy Systemxe2x80x9d, teaches a portable non-invasive apparatus for electro-therapeutic stimulation of tissue and bone healing readily worn or carried by a patient, capable of generating an energy-efficient signal co-acting with a suitable transducer of the signal, thereby realizing portability and stimulating tissue and bone healing. The teachings of the above-mentioned applications relate primarily to the stimulation of bone healing.
U.S. Pat. No. 6,321,119 to Kronberg, entitled xe2x80x9cPulsed Signal Generator For Bioelectric Stimulation And Healing Accelerationxe2x80x9d, teaches a pulsed signal generator for biomedical applications, including electrical stimulation of fracture healing, treatment of osteoporosis, strengthening of freshly-healed bone after removal of a cast or other fixation device, and iontophoresis. The generator includes dual asymmetric oscillators and associated circuitry to deliver signals efficiently throughout the area to be treated. The components of the generator are selected so as to produce any desired output signal, including fixed and variable amplitude, fixed, variable, and swept frequency signals, and DC biasing.
Although the teachings of U.S. Pat. No. 6,321,119 are directed primarily to bone healing and pain reduction (similar to TENS), it is noted that electrical stimulation can also produce a wide range of responses in other body systems, that the frequency and timing of the signal waveform appear to have some bearing on which body systems are more affected.
It is further noted that
xe2x80x9cit appears possible that appropriately-designed waveforms may prove useful for stimulating muscles, such as those in fractured and immobilized limbs or those of temporarily paralyzed persons, to help prevent atrophy and preserve muscle tone. Other applications may include stimulation of the endocrine glands and the immune system. For example, autoimmune conditions such as arthritis may be susceptible to localized, bioelectric immunosuppression without affecting the ability of the body as a whole to throw off infection. Much more research will be needed in order to evaluate the potential of such effects in healing or in the treatment of diseases, and to determine the optimum waveform for each application.xe2x80x9d
Thus, though is evident from U.S. Pat. No. 6,321,119 to Kronberg that appropriately-designed waveforms for stimulating muscles would be desirable, there is no practical instruction regarding the specific nature of the waveform, nor regarding the treatment procedure.
U.S. patent application No. 20020016618 to Da Silva, et al., entitled: xe2x80x9cIntegrated Cast And Muscle Stimulation Systemxe2x80x9d, teaches a device that allows electrical stimulation to an anatomical site that is covered by a cast. The electrode is applied to achieve a desired physiological response (e.g., bone growth), treatment of pain, or the prevention of muscle atrophy.
It is further disclosed that:
xe2x80x9cin normal use, the electrode module would only be used continuously for the first few days to block or reduce pain. After that time, electrode modules would only be applied several times a day for 10-20 minutes to stimulate the muscles and reduce muscular atrophy. Initially, the intensity of muscle stimulation would be low in order to prevent putting too much stress on the fracture. As the fracture heals, stimulation is increased to ensure that muscle tone is maintained during the one to three month healing period. The electrical stimulation unit can be preprogrammed to deliver a physician prescribed intensity pattern throughout the entire healing period.
Like U.S. Pat. No. 6,321,119 to Kronberg, U.S. patent application No. 20020016618 to Da Silva, et al., does not provide practical instruction regarding specific wave forms, patterns, and intensities for effective stimulation of cast-immobilized muscles. With regard to a treatment procedure, it is generally stated that electrically-induced stimulation of the affected muscle tissue should be applied several times a day for 10-20 minutes, in order to reduce muscular atrophy.
In the absence of practical direction with regard to effective stimulation of cast-impaired or cast-immobilized muscles, it would be highly advantageous to have a method for preventing muscular atrophy of such muscles, using electrical stimulation. It would be of further benefit for this method to be painless and convenient to apply. Finally, it would be highly advantageous to have a method that is applied by the patient in a safe, reliable, and effective manner, such that substantially no professional supervision is required, and can be effected automatically, without any special attention on the part of the patient.
The present invention is a safe, effective, and reliable method of stimulating muscles in a cast-immobilized limb in order to inhibit muscle atrophy.
According to the teachings of the present invention there is provided, a method of electrically stimulating muscles in a cast-bearing limb so as to inhibit muscle atrophy, the method including the steps of: (a) providing a system including: (i) at least two electrodes; (ii) a signal generator operatively connected to the electrodes, and (iii) a power source providing power to the signal generator; (b situating the electrodes in contact with tissue on the cast-bearing limb; (c) stimulating the muscles by externally inducing a percutaneous flow of electrical current between the electrodes through the tissue by establishing a plurality of external bipolar voltage waves across the electrodes, the plurality of bipolar voltage waves defining a treatment period, and (d) applying, over a 24-hour period, at least 12 distinct treatment periods.
According to further features in the described preferred embodiments, the treatment periods are administered during at least 10 hours of a 24-hour period, more preferably, during at least 16 hours of a 24-hour period, and most preferably, during at least 24 hours of a 24-hour period.
According to further features in the described preferred embodiments, the treatment periods are separated by rest periods having zero voltage applied between the electrodes, and wherein each of the rest periods is less than 12 hours.
According to further features in the described preferred embodiments, each of the rest periods is less than 6 hours, and most preferably less than 1 hour.
According to further features in the described preferred embodiments, the bipolar voltage waves have a frequency of less than 20 Hz, preferably less than 5 Hz. Most preferably, the voltage waves have a frequency in a range of 0.5-2.5 Hz.
According to further features in the described preferred embodiments, the treatment periods have a duration of less than 300 seconds.
According to further features in the described preferred embodiments, the treatment periods have a duration of less than 180 seconds.
According to further features in the described preferred embodiments, the treatment periods have a duration in a range of 30-120 seconds.
According to further features in the described preferred embodiments, the treatment periods are applied 4-20 times per hour.
According to further features in the described preferred embodiments, the treatment periods are applied 8-16 times per hour.
According to further features in the described preferred embodiments, the bipolar voltage waves have a varying frequency.
According to further features in the described preferred embodiments, the bipolar voltage waves have a frequency varying between 0.5-2.5 Hz.
According to further features in the described preferred embodiments, the bipolar voltage waves have a frequency varying by a factor of 1.2-4.0.
According to further features in the described preferred embodiments, the bipolar voltage waves have a frequency varying by a factor of 1.5-2.5.
According to further features in the described preferred embodiments, the ratio defined by a length of said treatment period divided by a length of one of said rest periods is less than 0.5, preferably less than 0.3, and most preferably in the range of 0.1-0.25.